Steel strand pre-tensioning method prestressed anchoring system and construction method thereof

Abstract

This invention discloses a prestressed anchorage system using pre-tensioned steel strands and its construction method. The system includes an upper anchor head, steel strands, a stabilizing plate, an isolation pipe, a central pressure bar, and a lower anchor head. The steel strands pass sequentially through the lower anchor head, the stabilizing plate, and the upper anchor head, with both ends connected to the upper and lower anchor heads respectively. The stabilizing plate is installed at intervals on the steel strands and fixedly connected to them. A through hole is provided in the center of the stabilizing plate, through which the isolation pipe passes. The central pressure bar passes through the isolation pipe. This invention utilizes steel strands and anchorages to form a self-balancing pre-tensioned steel strand prestressed anchorage system with the central pressure bar. This system offers secure anchorage, reliable performance, high material utilization, and convenient and quick on-site construction. The pre-tensioned steel strand prestressed anchorage system using a pressure release device allows for rapid release of large-tonnage prestress and steel strand tensioning. Construction is convenient, quick, and efficient. The tensioning platform and jacks can be removed after tensioning, improving equipment utilization.

Description

Technical Field

[0001] This invention belongs to the field of prestressed anchorage systems, and particularly relates to a prestressed anchorage system using steel strand pretensioning and its construction method. Background Technology

[0002] Currently in the field of bridge engineering, in order to improve the crack resistance of concrete components and avoid premature cracking of reinforced concrete components, prestress is applied to the concrete components during prefabrication to improve their performance. Among them, the pre-tensioning method involves tensioning steel strands before pouring the concrete component and temporarily anchoring the tensioned steel strands to the pedestal or steel mold. Then, the concrete is poured, and after the concrete component has cured to a strength of not less than 75% of the design strength of the concrete, ensuring sufficient bonding between the prestressing tendons and the concrete, the prestressing tendons are released. The prestressing is then applied to the concrete by relying on the bond between the concrete and the prestressing tendons.

[0003] Because the pre-tensioned prestressed anchorage system tensions the steel strands before pouring concrete components, a supporting structure is needed in the anchorage system to keep the steel strands in a tensioned state. For example, Chinese Patent Application No. 201920317746.3 discloses a prestressing reaction device for manufacturing pre-tensioned prestressed double-T beams. It uses force-transmitting steel pipes set on both sides as supporting structures to provide axial support force for the prestressed steel strands to form a self-balancing prestressing system. However, the following problems exist: the force-transmitting beam, force-transmitting steel pipes, jacks, steel strands, and anchors form a self-balancing system with low material strength per unit weight, a large system size, low utilization rate, and difficulty in on-site fabrication; the tensioning equipment cannot be removed before the system is released, resulting in low equipment utilization efficiency; and there is no relative constraint between the steel strands and the force-transmitting steel pipes, making it difficult to adapt to curved prestressed tendons. Another Chinese patent application with application number 200410045435.4 discloses a high-strength steel wire prestressed anchoring system and its construction method. This device achieves prestressed anchoring through steel wire pier anchoring. However, the device only uses steel wire piers for anchoring, which poses a risk of anchoring failure when using high-strength steel wire for prestressed anchoring. Therefore, a steel strand prestressed anchoring system and its construction method are needed. This system forms a self-balancing anchoring system through a central compression bar, which ensures anchoring safety, reliable performance, high material utilization, and convenient and quick on-site construction. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a prestressed anchorage system using pre-tensioned steel strands and its construction method, which can solve the problems of low anchorage reliability, difficulty in adapting to on-site construction, low equipment utilization, and difficulty in adapting to curved prestressed tendons in existing technologies.

[0005] The present invention is achieved through the following technical solutions.

[0006] This invention provides a prestressed anchoring system using pre-tensioned steel strands, comprising an upper anchor head, steel strands, a stabilizing plate, an isolation tube, a central pressure bar, and a lower anchor head. The steel strands pass sequentially through the lower anchor head, the stabilizing plate, and the upper anchor head, with both ends of the steel strands connected to the upper and lower anchor heads respectively. The stabilizing plate is installed at intervals on the steel strands and is fixedly connected to them. A through hole is provided in the middle of the stabilizing plate, through which the isolation tube passes. The central pressure bar passes through the isolation tube, with both ends of the central pressure bar pressing against the inner sides of the upper and lower anchor heads respectively.

[0007] The upper anchor head is equipped with an anchor plug, which is connected to the upper anchor head by a thread, and one end of the central pressure bar rests against the inside of the anchor plug.

[0008] The number of steel strands is at least three, and the steel strands are arranged in a circular array around the axis of the central pressure bar. The number and spacing of the stabilizing plates 3 are based on Euler's formula F. CR =π 2 EΙ / (μl) 2 The determination was made after system stability verification.

[0009] The central pressure bar includes a steel bar A, which is inserted into the isolation tube, with both ends of the steel bar A pressing against the inner sides of the upper and lower anchor heads, respectively.

[0010] The central pressure bar also includes a pressure release device, which is located in the middle of steel bar A. Steel bar A is divided into two sections, and the steel bars A are connected to each other through the pressure release device.

[0011] The pressure relief device includes a winding steel wire and multiple steel rods B. The multiple steel rods B are stacked parallel to each other to form a steel rod bundle, and the gaps between the steel rods B are filled with filler material. The winding steel wire is wrapped around the outer periphery of the steel rod bundle, and the two ends of the winding steel wire are welded to the steel rods B or welded to the winding steel wire.

[0012] The steel bars B are arranged in a regular hexagonal or circular shape, located in the middle of steel bar A, and both ends of steel bar B are connected to steel bar A.

[0013] The construction method of the prestressed anchorage system using pre-tensioned steel strands is characterized by the following steps:

[0014] Step S1: Cut the steel strands according to the length of the prestressing tendons provided in the design. The number of steel strands must be greater than or equal to 3. Insert the lower anchor head, stabilizing plate and upper anchor head into the steel strands. The number of stabilizing plates is calculated according to the Euler stability formula.

[0015] Step S2: Insert the isolation tube and the central pressure rod into the middle of the stabilizing plate. If the central pressure rod is equipped with a pressure release device, a release operation hole needs to be opened at the corresponding position of the isolation tube. After the isolation tube and the central pressure rod are installed, screw the anchor plug into the upper anchor head.

[0016] Step S3: Under the action of the tensioning platform and dry jack, the steel strand is elongated to form prestress between the lower anchor head and the upper anchor head;

[0017] Step S4: Remove the tensioning platform and jacks, and place the central pressure bar on the middle of the upper and lower anchor heads to counteract the tension of the steel strands and realize the pre-tensioned prestressed self-balancing system.

[0018] Step S5: Before pouring concrete, place the prestressed self-balancing system into the pouring mold. After the concrete reaches the design strength, unscrew the anchor plug, remove the central pressure rod from the isolation tube, and finally grout the isolation tube.

[0019] In step S5, if the central pressure bar does not have a pressure release device, the anchor plug is directly unscrewed to release the prestress of the steel strand, and then the central pressure bar is removed. If the central pressure bar has a pressure release device, the drill bit is inserted into the release operation hole to break the winding steel wire, causing the steel bar B to bend laterally, releasing the pressure of the steel bar, and then the anchor plug is unscrewed to release the prestress of the steel strand, and the central pressure bar is removed.

[0020] In step S3, when the steel strands are elongated, each individual steel strand is pre-tightened first, and then the whole strands are tensioned synchronously. The length and tension of each steel strand are the same.

[0021] The beneficial effects of this invention are as follows: The pre-tensioning prestressed anchorage system, formed by steel strands, anchorages, and a central compression bar, provides a self-balancing structure. This ensures anchorage safety, reliable performance, high material and equipment utilization, and convenient and rapid on-site construction. The pre-tensioning prestressed anchorage system using a pressure release device allows for rapid release of large-tonnage prestress and steel strand tensioning, making construction convenient, fast, and efficient. The tensioning platform and jacks can be removed after tensioning, further improving equipment utilization. Attached Figure Description

[0022] Figure 1 It is a prestressed anchoring system without pressure relief device 8;

[0023] Figure 2 It is a prestressed anchoring system with a pressure relief device 8;

[0024] Figure 3 yes Figure 1 Cross-sectional view at position A in the middle;

[0025] Figure 4 yes Figure 1 Cross-sectional view at position B in the middle;

[0026] Figure 5 yes Figure 2 Cross-sectional view at position C;

[0027] Figure 6 This is a cross-sectional view of the pressure relief device;

[0028] Figure 7 This is a schematic diagram of a pressure relief device;

[0029] Figure 8 This is a force analysis diagram of the prestressed anchorage system in the axial direction;

[0030] Figure 9 This is a stress analysis diagram of the prestressed anchorage system in the lateral direction;

[0031] Figure 10 This is a schematic diagram showing the transverse bending of steel bar B after the winding wire is broken.

[0032] In the diagram: 1-Upper anchor head, 2-Steel strand, 3-Stabilizing plate, 4-Anchor plug, 5-Isolation pipe, 6-Central pressure bar, 7-Lower anchor head, 8-Pressure release device, 9-Release operation hole, 10-Wound steel wire, 11-Steel bar B, 12-Filling material, 13-Concrete, 15-Steel bar A. Detailed Implementation

[0033] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0034] like Figures 1 to 10 As shown, a prestressed anchoring system using pre-tensioned steel strands includes an upper anchor head 1, steel strands 2, a stabilizing plate 3, an isolation pipe 5, a central pressure rod 6, and a lower anchor head 7. The steel strands 2 pass sequentially through the lower anchor head 7, the stabilizing plate 3, and the upper anchor head 1, with both ends of the steel strands 2 connected to the upper anchor head 1 and the lower anchor head 7, respectively. The stabilizing plate 3 is installed on the steel strands 2 at intervals and is fixedly connected to the steel strands 2. The stabilizing plate 3 has a through hole in the middle, through which the isolation pipe 5 passes. The central pressure rod 6 passes through the isolation pipe 5, with both ends of the central pressure rod 6 pressing against the inner sides of the upper anchor head 1 and the lower anchor head 7, respectively.

[0035] After the steel strand 2 is tensioned, the upper anchor head 1 and the lower anchor head 7 are pulled towards the center. At this time, the two ends of the central compression bar 6 respectively press against the upper anchor head 1 and the lower anchor head 7, counteracting the movement tendency of the upper anchor head 1 and the lower anchor head 7. At the same time, after the steel strand 2 is tensioned, when the stabilizing plate 3 encounters a lateral force, it can be counteracted by the tension of the steel strand 2. In turn, the stabilizing plate 3 can constrain the central compression bar 6, so that when the steel strand 2 is tensioned, the central compression bar 6 supports the upper anchor head 1 and the lower anchor head 7 along the axial direction, forming a self-balancing prestressed anchorage system using the pre-tensioned steel strand method. The anchorage is safe, the performance is reliable, the material utilization rate is high, and the on-site construction is convenient and quick.

[0036] The upper anchor head 1 is provided with an anchor plug 4, which is connected to the upper anchor head 1 by a thread. One end of the central pressure rod 6 is pressed against the inside of the anchor plug 4. After the anchor plug 4 is unscrewed, it is convenient to insert the isolation tube 5 and the central pressure rod 6. During tension release, the central pressure rod 6 can be released by unscrewing the anchor plug 4, so that the prestress of the steel strand can be released.

[0037] The number of steel strands 2 is at least 3. The steel strands 2 are arranged in a circular array around the axis of the central pressure bar 6, so that the tension of the steel strands 2 can be evenly applied to the upper anchor head 1 and the lower anchor head 7, and the central pressure bar 6 can bend due to uneven force during self-balancing. The number and spacing of the stabilizing plates 3 are based on Euler's formula F. CR =π 2 EΙ / (μl) 2 The system stability was checked and determined. In the formula, E is the elastic modulus; I is the moment of inertia of the cross section; μ is the length factor; and l is the length of the compression member.

[0038] Example: Steel strand: Quantity 3 strands, nominal diameter 15.2mm, nominal strength 1860MPa (nominal breaking force 260kN);

[0039] If the tension of the steel strand is 0.75 times the nominal breaking force, then the total tension of the steel strand is F = 3 * 260 * 0.75 = 585 kN;

[0040] The diameter D of the pressure bar is 50 mm, and the length l is 3000 mm;

[0041] Analysis: Moment of inertia of the cross section I = πD 2 / 64=3.066×10 -7 m 4 ;

[0042] According to the table, μ = 1;

[0043] E = 210 GPa;

[0044] Without a stabilizing plate, the critical pressure F of the compression bar CR =π 2 EΙ / (μl) 2 =70.54kN;

[0045] To satisfy self-balancing stability: F CR ≥F;

[0046] The number of stabilizer plates 3 needs to be increased:

[0047] When the number of stabilizing plates 3 is increased to 2, the pressure bar can be considered as being divided into 3 segments by the stabilizing plates 3. Therefore, l decreases to l / 3, i.e., l = 1000 mm.

[0048] The critical pressure F of the compression barCR =π 2 EΙ / (μl / 3) 2 =634.86kN>F, which meets the stability requirements. The safety factor n = 634.86 / 585 = 1.08;

[0049] When the increase is 3, then l decreases to l / 4.

[0050] The critical pressure F of the compression bar CR =π 2 E1 / (μl / 4) 2 =1128.64kN>F, which meets the stability requirements, and the safety factor n=1128.64 / 585=1.93;

[0051] When the increase is 4, then l decreases to l / 5.

[0052] The critical pressure F of the compression bar CR =π 2 E1 / (μl / 5) 2 =1763.5kN>F, which meets the stability requirements. The safety factor n = 1763.5 / 585 = 3.

[0053] Therefore, the more stabilizers you add, the safer and more reliable the system becomes.

[0054] The central pressure bar 6 includes a steel bar A15, which is inserted into the isolation tube 5. The two ends of the steel bar A15 are respectively pressed against the inner sides of the upper anchor head 1 and the lower anchor head 7. For the prestressed anchoring system with a small tension of the steel strand 2, the tension of the steel strand 2 is small during release, and release can be achieved by a single steel bar A15.

[0055] The central pressure bar 6 also includes a pressure release device 8, which is located in the middle of the steel bar A15. The steel bar A15 is divided into two sections, and the steel bars A15 are connected to each other through the pressure release device 8. For the prestressed system of large-tonnage steel strands, the energy released during release is relatively large. Therefore, it is necessary to release the tension first through the pressure release device 8, and then release the tension again after unscrewing the anchor plug 4 before removing the central pressure bar 6.

[0056] like Figure 10As shown, the pressure relief device 8 includes a wound steel wire 10 and multiple steel rods B11. The multiple steel rods B11 are stacked parallel to each other to form a steel rod bundle, and the gaps between the steel rods B11 are filled with a filler material 12. The wound steel wire 10 is wound around the outer periphery of the steel rod bundle, and both ends of the wound steel wire 10 are welded to the steel rods B11. The filler material 12 is a material with a low elastic modulus, such as polyurethane. The wound steel wire 10 is wound around the outer periphery of the steel rod bundle, and both ends of the wound steel wire 10 are welded to the steel rods B11 or to the wound steel wire 10 itself. After the winding wire 10 is wound, the steel rods B11 are tightly attached. When the steel rods B11 are subjected to the pressure of the steel rod A15, the steel rods B11 restrain each other to form a stable structure, which cannot bend laterally, thus ensuring the strength of the steel rod A15 and forming a self-balancing system. When it is necessary to release the tension, the winding wire 10 is broken with a drill bit. After the steel rod bundle loses the pressure provided by the winding wire 10, the steel rods B11 loosen and bend laterally. At this time, the length of the steel rod A15 is shortened, and the force on the steel rod A15 is released through the bending of the steel rods B11.

[0057] The steel bars B11 are arranged in a hexagonal or circular pattern, located in the middle of steel bar A15, with both ends of steel bar B11 connected to steel bar A15. Multiple steel bars B11, bound together by the winding wire 10, can form a single unit. When pressure is applied to both ends of steel bars B11, the multiple steel bars B11 mutually restrain each other, preventing significant bending and thus counteracting the movement tendency of steel bar A15, forming a self-balancing system. The hexagonal or circular arrangement of the steel bars B11 facilitates winding, and the mutual restraint among the steel bars B11 forms a stable structure.

[0058] The construction method of the prestressed anchorage system using pre-tensioned steel strands is characterized by the following steps:

[0059] Step S1: Cut the steel strand 2 according to the length of the prestressing tendon provided in the design. The number of steel strand 2 must be greater than or equal to 3. Insert the lower anchor head 7, the stabilizing plate 3 and the upper anchor head 1 into the steel strand 2. The number of stabilizing plates 3 is calculated according to the Euler stability formula.

[0060] Step S2: Insert the isolation tube 5 and the central pressure rod 6 through the middle of the stabilizing plate 3. If the central pressure rod 6 is equipped with a pressure release device 8, a release operation hole 9 needs to be opened at the corresponding position of the isolation tube 5. After the isolation tube 5 and the central pressure rod 6 are installed, screw the anchor plug 4 into the upper anchor head 1. Use the central pressure rod 6 to support the upper anchor head 1 and the lower anchor head 7 to achieve a self-balancing system. At the same time, the stabilizing plate 3 provides lateral support to prevent the central pressure rod 6 from bending during support.

[0061] Step S3: Under the action of the tensioning platform and the dry jack, the steel strand 2 is stretched, and prestress is formed between the lower anchor head 7 and the upper anchor head 1, so that the steel strand 2 is in a stretched state, so as to increase the tension after being embedded in the concrete and give the concrete prestress.

[0062] Step S4: Remove the tensioning platform and jacks. The central pressure bar 6 is placed on the middle of the upper anchor head 1 and the lower anchor head 7 to counteract the tension of the steel strand 2, thus realizing the pre-tensioned prestressed self-balancing system. When the tension of the steel strand 2 is counteracted by the central pressure bar 6, the upper anchor head 1, and the lower anchor head 7, forming a self-balancing system, only one central pressure bar 6 is needed, resulting in high material utilization.

[0063] Step S5: Before pouring concrete 13, place the prestressed self-balancing system into the pouring mold. After the concrete reaches the design strength, unscrew the anchor plug 4, remove the central pressure bar 6 from the isolation tube 5, and finally grout the isolation tube 5 to release the tension of the steel strand 2 so as to apply pressure in the concrete and form a prestressed concrete component.

[0064] In step S5, if the central pressure bar 6 does not have a pressure release device 8, the anchor plug 4 is directly unscrewed to release the prestress of the steel strand 2, and then the central pressure bar 6 is removed. If the central pressure bar 6 has a pressure release device 8, a drill bit is inserted into the release operation hole 9 to break the winding steel wire 10, causing the steel bar B11 to bend laterally, releasing the pressure on the steel bar, and then the anchor plug 4 is unscrewed to release the prestress of the steel strand, and the central pressure bar 6 is removed. For the prestressed system of large-tonnage steel strands, the energy released during release is large, so it is necessary to release the tension first through the pressure release device 8, and then unscrew the anchor plug 4 to remove the central pressure bar 6.

[0065] In step S3, when the steel strand 2 is elongated, the individual steel strand 2 is pre-tightened first, and then the whole strand is tensioned synchronously. The length and tension of each steel strand are the same, so that the pressure applied by the upper anchor head 1 and the lower anchor head 7 to the central pressure bar 6 can be balanced, and the stabilizing plate 3 can also provide lateral support to the central pressure bar 6.

Claims

1. A prestressed anchorage system using pre-tensioned steel strands, characterized in that: The system includes an upper anchor head (1), steel strands (2), a stabilizing plate (3), an isolation pipe (5), a central pressure rod (6), and a lower anchor head (7). The steel strands (2) pass through the lower anchor head (7), the stabilizing plate (3), and the upper anchor head (1) in sequence, and the two ends of the steel strands (2) are connected to the upper anchor head (1) and the lower anchor head (7) respectively. The stabilizing plate (3) is installed on the steel strands (2) at intervals and is fixedly connected to the steel strands (2). The stabilizing plate (3) has a through hole in the middle, through which the isolation pipe (5) passes. The central pressure rod (6) passes through the isolation pipe (5), and the two ends of the central pressure rod (6) are respectively pressed against the inner sides of the upper anchor head (1) and the lower anchor head (7). The upper anchor head (1) is provided with an anchor plug (4), which is connected to the upper anchor head (1) by a thread, and one end of the central pressure rod (6) is pressed against the inside of the anchor plug (4); The central pressure bar (6) includes a steel bar A (15), which is inserted into the isolation tube (5), and the two ends of the steel bar A (15) are respectively pressed against the inner sides of the upper anchor head (1) and the lower anchor head (7); The central pressure bar (6) also includes a pressure release device (8), which is located in the middle of the steel bar A (15). The steel bar A (15) is divided into two sections, and the steel bars A (15) are connected to each other through the pressure release device (8). The pressure relief device (8) includes a winding steel wire (10) and multiple steel rods B (11). The multiple steel rods B (11) are stacked parallel to each other to form a steel rod bundle, and the gaps between the steel rods B (11) are filled with filler material (12). The winding steel wire (10) is wound around the outer periphery of the steel rod bundle, and the two ends of the winding steel wire (10) are welded to the steel rods B (11) or welded to the winding steel wire (10).

2. The prestressed anchorage system using pre-tensioned steel strands as described in claim 1, characterized in that: The number of steel strands (2) is at least 3. The steel strands (2) are arranged in a ring array with the axis of the central pressure bar (6) as the center. The number and spacing of the stabilizing plates (3) are based on Euler's formula. The determination was made after system stability verification.

3. The prestressed anchorage system using pre-tensioned steel strands as described in claim 1, characterized in that: The steel bars B(11) are arranged in a regular hexagonal or circular shape. The steel bars B(11) are located in the middle of the steel bars A(15), and both ends of the steel bars B(11) are connected to the steel bars A(15).

4. A construction method for a prestressed anchorage system using pre-tensioned steel strands as described in any one of claims 1 to 3, characterized by the following steps: Step S1: Cut the steel strands (2) according to the length of the prestressing tendons provided in the design. The number of steel strands (2) must be greater than or equal to 3. Insert the lower anchor head (7), the stabilizing plate (3) and the upper anchor head (1) into the steel strands (2). The number of stabilizing plates (3) is calculated according to the Euler stability formula. Step S2: Insert the isolation tube (5) and the central pressure rod (6) into the middle of the stabilizing plate (3). If the central pressure rod (6) is equipped with a pressure release device (8), a release operation hole (9) needs to be opened at the corresponding position of the isolation tube (5). After the isolation tube (5) and the central pressure rod (6) are installed, screw the anchor plug (4) into the upper anchor head (1). Step S3: Under the action of the tensioning platform and dry jack, the steel strand (2) is stretched to form prestress between the lower anchor head (7) and the upper anchor head (1); Step S4: Remove the tensioning platform and jacks, and place the central pressure bar (6) against the middle of the upper anchor head (1) and the lower anchor head (7) to counteract the tension of the steel strand (2) and realize the prestressed self-balancing system of the pre-tensioning method. Step S5: Before pouring concrete (13), place the prestressed self-balancing system into the pouring mold. After the concrete reaches the design strength, unscrew the anchor plug (4), take out the central pressure bar (6) from the isolation tube (5), and finally grout in the isolation tube (5). If the central pressure bar (6) does not have a pressure release device (8), unscrew the anchor plug (4) directly to release the prestress of the steel strand (2), and then remove the central pressure bar (6). If the central pressure bar (6) has a pressure release device (8), insert the drill bit into the release operation hole (9) to break the winding steel wire (10), so that the steel bar B (11) bends laterally to release the pressure of the steel bar. Then unscrew the anchor plug (4) to release the prestress of the steel strand and remove the central pressure bar (6).

5. The construction method of the prestressed anchorage system using pre-tensioned steel strands as described in claim 4, characterized in that: In step S3, when the steel strand (2) elongates, the individual steel strand (2) is pre-tightened first, and then the whole strand is tensioned synchronously. The rope length and tension of each steel strand are the same.

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